Method of making continuous  filament reinforced structural plastic profiles using pultrusion/coextrusion

ABSTRACT

A system and method are disclosed for producing a continuous filament reinforced thermoplastic profile having consistent cross section. A continuous reinforcing filament is pre-wetted with a first thermoplastic resin and introduced into a die, where it is contacted with a second thermoplastic resin extruded from an extruder at melt state. The temperature of the die is carefully controlled so that the pre-wetted filament and first resin do not cure or solidify until after they have contacted and mixed with the second thermoplastic resin. The mixture temperature is then controlled to make a substantially solidified profile pre-shape. A capping layer comprising a third thermoplastic resin is then co-extruded onto the outer surface of the pre-shape. A multistage die for bringing together the filament and thermoplastic resins and for maintaining appropriate temperatures at each stage of the profile-forming process is also disclosed.

FIELD OF THE INVENTION

The invention relates to reinforced plastic composite materials andmethods for their manufacture, and more particularly to improvedcontinuous filament reinforced thermoplastic products and methods fortheir manufacture.

BACKGROUND OF THE INVENTION

Current residential and commercial fence and rail materials are made oftraditional lumber, metal or polymers including thermoplastics. Typicalthermoplastics used in these applications are PVC (polyvinyl chloride)and polyolefins such as polyethylene and polypropylene. Thermoplasticstypically do not have the strength and rigidity of wood and lumber and,therefore, the rail for the fence and railing needs a steel or aluminumreinforcement channel inside the rail. Metal fence and rail materials,as well as the metal reinforcements used with current PVC fence and railmaterials, are prone to corrosion attack, and lose strength in long-termendurance tests. Additionally, where dark-colored thermoplasticsmaterials are employed, thermal expansion problems can arise due todifferences in expansion between opposing sides of the product when theproduct is exposed to sunlight. Since the dark color absorbs heat morereadily on the sun-facing side of the product, the resultant uneven heatbuildup causes the rail to deform. An additional problem is the lack oflong-term stiffness of polymeric products, which has limited the railspan between the posts to lengths less than traditional lumber andmetallic rails.

One solution to the stiffness problem is to add filaments to thethermoplastic resin during manufacturing. These filaments typically areadded as small-length (e.g., less than Y2-inch long) chopped filamentsmade of any of a variety of materials. The resulting thermoplasticprofiles can have increased strength and stiffness as compared toun-reinforced profile products. Typically, the short-filamentreinforcement is achieved using extrusion techniques. Alternatively,continuous or long filament reinforcement of thermosetting andthermoplastic profiles has been achieved using pultrusion processes.

Conventional continuous filament reinforced thermoplastic profileproducts produced using conventional pultrusion processes still sufferfrom deficiencies in mechanical properties in the cross direction (e.g.,flexural strength, tensile strength, impact strength, and compressionstrength), due typically to poor bonding between the substrate resin andthe filaments. This poor bonding is primarily due to poor resin wet-outof the filaments by the resin. Thus, for applications using mechanicalfasteners, the profile products have low screw and nail holding power.Additionally, cracking, splitting and separation of filaments in theseprofiles can easily occur during transportation, application, andinstallation.

As a result, in order to achieve desired high mechanical strengthlevels, filament reinforced thermoplastics profiles produced usingconventional pultrusion processes, are designed to have thicker walls,and/or higher glass filament loading. Both of these approaches mayresult in a higher than desirable profile weight.

Additionally, conventional pultrusion processes for incorporating longfilaments are relatively slow, and thus result in an undesirably lowoutput rate (e.g., frequently on the order of only 2-3 feet per minute).The slowness of the process is due to the time required for (1) meltingof the thermoplastics, and (2) wet-out of the melted thermoplasticsaround the filaments. Filament wet-out with thermoplastic resin istypically poor, even at higher temperature and longer residence times,due to the relatively high viscosity of thermoplastic materials.Further, incompatibility between the thermoplastic resin and thefilament material can also lead to poor wet-out.

Thus, to achieve a desired total production rate with current pultrusionprocesses, additional machines must be employed. The additionalmachines, however, take up additional manufacturing floor space andinvolve larger amounts of capital investment, thus leading to increasedcosts.

Alternatively, conventional filament reinforced thermoplastic profileproducts produced using conventional extrusion processes suffer fromdeficiencies in mechanical properties in the cross direction becausecurrent processes only allow for the incorporation of very shortfilament lengths. This is because conventional extrusion of longfilament reinforced thermoplastic profile products typically involvesthe use of an intermeshing twin screw extruder, whose intermeshingscrews act like scissors which chop the filaments to short lengths,regardless of the length of the filaments added to the resin. Suchprocesses can result in filament lengths of about one tenth of theiroriginally added length. Where discrete-length filaments (in lieu ofcontinuous filaments) are introduced into the extrusion flow, originalfilament lengths are limited to about ½-inch or shorter in length. Ifthe filament length is too long (i.e., over ½-inch), the filaments willform a bridge at the introduction hopper, clogging the hopper andinhibiting feeding of the filaments into the extruder. Where filamentsof less than ½-inch in length are used, the intermeshing twin screws canchop the filaments to even shorter length. Such short filament lengthsare undesirable for use as reinforcement for thermoplastic productsbecause they do not provide the enhanced strength that is desired.Additionally, filament loading using such processes is low.

Thus, there is a need for high strength thermoplastics products whichincorporate a long or continuous filament reinforcement scheme. There isalso a need for a process for producing such products in a fast andeconomical manner so as to make high-strength reinforced productscommercially viable.

SUMMARY OF THE INVENTION

A method is disclosed for manufacturing a reinforced thermoplasticstructure. The method may comprise: providing a plurality of reinforcingfilaments; wetting the reinforcing filaments with a first thermoplasticresin; introducing the reinforcing filaments with the firstthermoplastic resin into a first portion of a die and maintaining saidthermoplastic resin at a first temperature; introducing a secondthermoplastic resin into a second portion of the die; contacting thesecond thermoplastic resin with the reinforcing filaments and the firstthermoplastic resin within the second portion of said die; heating thefirst and second thermoplastic polymer resins to a second temperature toallow the first resin (i.e. the one that wets the filament) to start toform a gel within the encapsulation of the second resin, or to form asemi-solidified reinforced thermoplastic structure having apredetermined outer shape; and contacting the reinforced thermoplasticstructure with a third thermoplastic resin to form a capping layer on anexterior surface of the reinforced thermoplastic structure. The firsttemperature may be a value below the solidification temperature of thefirst thermoplastic resin and the second temperature may be a valueabove the solidification temperature of the first, second or thirdthermoplastic resins.

A method for manufacturing a reinforced thermoplastic structure isdisclosed, comprising: providing a reinforcing filament; wetting thereinforcing filament with a first thermoplastic resin; introducing thereinforcing filament with the first thermoplastic resin into a firstportion of a die and maintaining said thermoplastic resin at a firsttemperature; introducing a second thermoplastic resin into a secondportion of the die; contacting the second thermoplastic resin with thereinforcing filament wetted by the first thermoplastic resin within thesecond portion of said die; transporting the first and secondthermoplastic polymer resins through the second portion of said diewhile forming the first and second thermoplastic polymer resins into areinforced thermoplastic structure having a predetermined outer shape;and exposing the reinforced thermoplastic structure to a zone having asecond temperature. The first temperature may be a temperature at whichthe first thermoplastic resin is in a stable liquid state and the secondtemperature is a value at which at least the first thermoplastic resincan partially form a gel or partially solidify.

A method for manufacturing a reinforced thermoplastic structure isdisclosed, comprising: providing a plurality of reinforcing filaments;wetting the reinforcing filaments with a first thermoplastic resin;introducing the reinforcing filaments with the first thermoplastic resininto a first portion of a die and maintaining said thermoplastic resinat a first temperature; introducing a second thermoplastic resin into asecond portion of the die; contacting the second thermoplastic resinwith the reinforcing filaments and the first thermoplastic resin withinthe second portion of said die; and heating the first and secondthermoplastic polymer resins to a second temperature to allow the firstresin to start to form a gel, or to start to form a semi-solidifiedreinforced thermoplastic structure having a predetermined outer shape.The first temperature may be a value below the solidificationtemperature of the first thermoplastic resin and the second temperaturemay be a value above the solidification temperature of the firstthermoplastic resin and above the molten temperature of the secondthermoplastic resin.

A method for manufacturing a reinforced thermoplastic structure isdisclosed, comprising: providing a plurality of reinforcing filaments;wetting the reinforcing filaments with a first thermoplastic resin at afirst temperature, said first temperature corresponding to asubstantially liquid state of said first thermoplastic resin;introducing the reinforcing filaments with the first thermoplastic resininto a first portion of a die; introducing a second thermoplastic resininto a second portion of the die; contacting the second thermoplasticresin with the reinforcing filaments and the first thermoplastic resinwithin the second portion of said die; and cooling the first and secondthermoplastic polymer resins to a second temperature to form a partiallysolidified reinforced thermoplastic structure having a predeterminedouter shape. The second temperature may be a value below thesolidification temperature of at least one of the first and secondthermoplastic resins.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of theinvention, as well as other information pertinent to the disclosure, inwhich:

FIG. 1 is a schematic view of a first exemplary pultrusion-coextrusionsystem according to the invention;

FIGS. 2A and 2B are front and reverse isometric views of a cross-headdie for use in the system of FIG. 1, showing the introduction ofreinforcing filaments and resins into the die, and the output of astructural profile from the die;

FIGS. 3A, B, C, D and E are isometric and cross-section views of anexemplary filament wetting system for use with the system of FIG. 1;

FIGS. 4A and 4B are exemplary filament alignment devices for use withthe filament wetting system of FIGS. 3A and 3B;

FIGS. 5A, B and C are a cross section views of an exemplary die for usewith the pultrusion-co-extrusion process of FIG. 1;

FIGS. 6A through 6K are end views of a variety of optional arrangementsfor filament channels in the die of FIG. 5;

FIGS. 7A through 7F are cross section views of a plurality of filamentreinforced profiles produced in accordance with the process of FIGS. 1and 2;

FIGS. 8A and 8B are schematic views of further embodiments of theprocess of FIG. 1, incorporating injection molding and compressionmolding steps.

DETAILED DESCRIPTION

Provided herein are a system and method for manufacturingcontinuous-filament reinforced thermoplastics profiles for use inresidential and commercial building applications. For the purposes ofthis application the term “profile” shall mean structural members suchas I-beams, planks, beams, columns, channels, such as, for example,C-channels, J-channels, F-channels, and the like, angles, and tubularshapes, window lineals, decking planks, railings, balusters, roofingtiles, siding, trim boards, soffiting, pipe, and the like, withoutlimitation. Additionally, the term “filaments” shall mean individualfilaments or fibers, or bundles of such filaments or fibers, such asroving, yarn, and rolls of mat, tape, felt or scrim. With reference tothe Figures, and more particularly to FIGS. 1, 2A and 2B, an exemplaryprocess for manufacturing a filament-reinforced thermoplastic profile isshown. A plurality of filaments 1 may be unwound from a plurality ofcreels 2 and passed through a filament wetting system 4 comprisingfilament alignment mechanisms 6, 8, 10 and a first thermoplastic resinwetting basin 12 which may pre-wet the filaments 1 with a firstthermoplastic resin 14. The pre-wetted filaments 1 may then be fed intoindividual filament channels 16 in crosshead die 18. The individualfilament channels 16 may be arranged within the die 18 to achieve aspecific placement of the reinforcing filaments within the ultimateprofile product 38. The individual filament channels 16 may also servegenerally to direct the wetted filaments 1 into a main portion of thecrosshead die 18 so that they may be brought into contact with a secondthermoplastic resin 22. The second resin 22 may be extruded at meltstate into the die 18 via a first extruder 24, to form a laminate orsandwich of resin 14, 22 and filaments 1, and to fill the die interiorwith thermoplastic resin. The pre-wetted filaments 1 and the secondthermoplastic resin 22 together may then be directed through a profiledie 26 to form a profile preshape 28. This profile preshape 28 mayapproximate the shape of the final profile.

The temperature and flow conditions within the crosshead die 18 may becarefully controlled, as will be discussed in more detail later, toensure adequate commingling of the pre-wetted filaments with the secondthermoplastic resin 22, and also to provide a graduated solidificationof the profile preshape 28 as it passes through the die 18. At or nearthe outlet 30 of the die 18, the profile preshape 28 may pass through aprofile die 26, (which may be part of the cross-head die 18 or it may bea separate die), where a third resin 34 with additives may beco-extruded onto the outer surface of the profile preshape 28 to form acap layer 36. The third resin 34 may be injected at melt state using asecond extruder 35. After the cap layer 36 has been applied, theresulting capped profile 38 may then pass though a calibrator 40 forshaping and sizing to adjust and control the dimensions and surfacetexture of the extrudate, followed by a cooling section 42, a pullingsection 44, and a cutting section 46 that may cut the capped profile toa predetermined length.

Although not shown, a fourth resin could be applied as a clear coatingto provide ultraviolet (UV) reflectance, wear resistance, wood grainpatterning, or other desired property. In one embodiment, this clearcoating would allow the color of the cap layer to be seen through thecoating. This clear coating could be applied in a subsequent coextrusionor extrusion coating step, or it could be spray applied or printed bycontacting or noncontacting means. The fourth resin may be a thermosetresin, such as epoxy, polyesters, phenolic resin, or it may be athermoplastic resin, including but not limited to, acrylic polymer orcopolymers, such as acrylic acid polymer, methacrylic acid copolymers(PMA), methyl methacrylic acid copolymers (PMMA), ethyl acrylic acidcopolymers (PEA), ethyl methacrylic acid copolymers (PEMA), butylacrylic acid copolymers (PBA), butyl methacrylic acrylic acid copolymers(PBMA), and/or the mixture of above, polyvinyl acetate, polyvinylalcohol, ethylene vinyl alcohol, fluorinated polymers and copolymers,polymers and copolymers of vinylidene fluoride, polyurethanes, maleicacid modified ethylene copolymers, maleic acid modified propylenecopolymers and metal ionomer salts, and/or mixtures or blends thereof.

Alternatively, the third or fourth layers could be applied as disclosedin copending U.S. patent application Ser. No. 11/247,620 to Jeng, titled“Building Material Having a Fluorocarbon Based Capstock Layer andProcess of Manufacturing Same with Less Dimensional Distortion,” filedOct. 11, 2005, the entirety of which is incorporated by referenceherein. The third, fourth, or yet subsequent layers could each in turncomprise sublayers, the sublayers being directed toward enhancing theaesthetics of and contributing to the weatherability of the finishedextrudate.

Additionally, although the process shown in FIG. 1 includes theapplication of a cap layer 36 to the profile preshape, the cap layer 36is optional, such as where the substrate profile possesses appropriateproperties for exterior or interior applications, such as resistance toenvironmental attack in the form of UV radiation, thermal impact, freezeand thaw cycles, rain storm, snow storm, hail, as well as resistance tochemicals such as acidic liquid or air, stains and the like. Thus, it isenvisioned that a reinforced profile product may be formed without a caplayer 36.

Advantageously, the extrudate (the thermoplastic matrix comprising thesecond thermoplastic resin 22 and optionally the third thermoplasticresin 34) is not allowed to fully solidify within the die 18, and thusprecise and accurate control of the final dimensions and surface textureof the profile 38 may be achieved by further processing downstream ofthe die 18. The solidification process for the thermoplastic matrix canbe precisely controlled by carefully controlling the temperature withinthe die 18, thus ensuring that the profile 38 continues to be shapeableand formable as it is introduced into the calibrator 40, which controlsthe final shape of the profile. This solidification process is alsoadvantageous because it prevents damage to the profile and/or the die,which could occur if the profile were to solidify fully within the die18. For example, since the interior surface of the die 18 changes shapealong the path of the extrudate (see FIG. 5A), full solidification ofthe profile within the die could cause the material to break, get stuck,or could cause the die to break.

The finished profile 38 may comprise a continuous filament-reinforcedengineered structural thermoplastic profile having a consistent crosssection, within which a plurality of reinforcing filaments are preciselylocated in order to maximize strength. The high strength of the finishedprofile 38 is attributable to the superior bonding between thepre-wetted continuous filaments 1 and the second thermoplastic resin 22.This high degree of bonding is achieved by selecting first and secondthermoplastic resins 14, 22 having close chemical compatibility witheach other, as well as with the cap (third) resin 34.

The individual portions of the system will now be discussed in greaterdetail.

The filament wetting system 4 may be arranged to provide a desired highdegree of wetting of the filaments 1 with the first resin 14 prior totheir introduction into the crosshead die 18. FIG. 3A shows a preferredarrangement for a filament pre-wetting system 4, including a resinwetting basin 12 and one or more filament alignment structures 51, whichin FIG. 3A comprise bars. Alternatively, planar filament alignmentstructures commonly referred to as “holly boards” 52 a, b, c (FIGS. 3B,3C, 4A, 4B) may be used in place of the bars 51. Thus, as shown in FIG.3C, the basin 12 may be filled with a quantity of substantially liquidfirst resin 14, and one or more holly boards 52 may be arranged insubstantially vertical alignment with respect to the surface of theliquid first resin. The basin 12 is optionally equipped with temperaturecontrol means (not shown) as is the path of the fibers 1 from the creels2 to the die system.

Again, referring to FIG. 3C, the holly boards 52 may advantageously beused to align the filaments 1 as they are unwound from the creels 2 andto direct the filaments below the surface of the first resin 14. Assuch, a first holly board 52 a may be positioned so that all of thefilaments 1 are above the level of the first resin 14, while the nextholly board(s) 52 b (or bar, or roller) may be positioned beneath thelevel of the first resin to ensure all of the filaments are submerged inthe first resin. The third holly board 52 c may again be positionedabove the level of the first resin 14. As such, the filaments 1 maytraverse a substantially V-shaped or U-shaped path through the resinbasin 12. It is noted that a U-shaped path may result in the filaments 1being submerged in the first resin 14 for a longer period of time thanwith a V-shaped path. Likewise, a W-shaped path (in which the filamentsare moved into the bath, out of the bath, and then back into the bath)could achieve a similar effect.

In one embodiment, the filaments 1 are glass fibers, and the first resin14 is a PVC plastisol. In another embodiment, the fibers are polymericfibers. In yet another embodiment, the resin is a high melt indexthermoplastic polymer, preferably a high melt index acid containingpolyolefin copolymer in a molten state. Such acid containing olefincopolymers include, but are not limited to, acrylic polymer orcopolymers such as methacrylic acid polymer, methyl methacrylic acidcopolymers, ethylene methacrylic acid copolymers, ethylene acrylic acidcopolymers, butyl acrylic acid copolymers, butyl methacrylic acidcopolymers, maleic acid modified ethylene copolymers, maleic acidmodified propylene copolymers and metal ionomer salts thereof.

As shown in FIGS. 3B, 4A, B, the holly boards 52 may each have aplurality of openings 54 for receiving individual filaments 1 or bundlesof filaments. These openings 54 may serve to align the filaments 1 andto prevent adjacent filaments from tangling with each other as they movefrom the creels 2 through the resin basin 12. The openings 54 may alsocontrol the total number filaments 1 that occupy a particular region ofthe resin basin to ensure that a maximum surface area of each filamentis exposed to the liquid first resin 14 for a desired amount of time, tothereby achieve adequate wetting of a maximum number of filaments. Theindividual openings 54 in the third holly board 52 c may be sized andshaped to squeeze excess resin from the surfaces of the filaments afterthe filaments have emerged from the first resin 14, and to return theexcess resin to the basin 12 for reuse. The openings 54 in the hollyboards 52 may be round (FIG. 4A), rectangular or slotted (FIG. 4B),square, elliptical, triangular, etc., or combinations thereof.

The arrangement of the holly boards 52 (i.e., their vertical andhorizontal positions with respect to each other) may be configured sothat, for a given line speed, the filaments 1 reside in contact with thefirst resin 14 for a sufficient time to provide a desired degree ofwetting. The residence time of the filaments 1 in the first resin ispreferably not less than 5 seconds, more preferably about 10 seconds,and most preferably about 20 seconds. Additionally, the angle α (FIG.3B) between the longitudinal axes of the filaments 1 and the verticalplanes of the individual holly boards 52 may be up to about 90-degrees,and preferably between about 0-degrees to about 50-degrees. Providing anangle α that approaches 0-degrees (i.e., a horizontal filament path)results in less friction and resistance to movement of the filaments 1through the holly boards 52.

One or more holly boards 52 may be used with a single basin 12.Alternatively, roller or bar elements 51 (FIGS. 3A, 3D, 3E) may be usedin place of one or more of the holly boards 52. In one embodiment,illustrated in FIG. 3C, where multiple holly boards are used in a singlebasin 12, the holly boards 52 b may be slidably mounted to the basin 12so that it may be moved up and down with respect to the level of thefirst resin 14 (in the direction of the arrows). This verticaladjustability may also be provided where rollers are used in lieu ofholly boards (see FIG. 3D). Providing such adjustability may allow theuser to control the amount of time the filaments 1 are in contact withthe first resin (i.e., the residence time), thus allowing the userenhanced control over the filament wetting process. It will beappreciated that this adjustability feature may be automated so that theuser can electronically control the positions of one or more of theholly boards, thus allowing automated control of the filament wettingprocess. For example, the level of the filaments 1 may be adjustedwithin the basin 12 to compensate for changes in the level of resin inthe basin, thus ensuring adequate filament wetting. Additionally,providing adjustable holly boards allows easy control of the wettingprocess during startup and shutdown of the system.

Furthermore, the arrangement of the openings 54 in the holly boards 52may be configured in specific geometric or other patterns to pre-alignthe filaments 1 in the same or similar arrangement to that of thefilament channels 16 in the die 18 and/or the filament placement in thefinal profile preshape 28 as desired.

As previously noted, one or more of the bars 51 or holly boards 52 maybe replaced by a suitable pair of opposing rollers 53 a, b having aknown gap “g” between them (see FIGS. 3D, 3E). The opposing rollers 53a, b may be used in a fashion similar to the holly boards 52 to directthe filaments 1 through the resin bath. Such an arrangement, whileproviding a degree of flexibility, may not provide the same control overfilament alignment as is obtainable with the holly board arrangement.This may be important because it can reduce the ability of the system toprevent filaments from bunching or clumping when they contact the firstresin 14, which can adversely affect the efficiency of the wettingprocedure. The use of rollers may, however, be advantageous when feedingmat, scrim or reinforcing tapes through the basin 12. Additionally, therollers may be provided with grooves on the roller surfaces to act as aguide for such flat reinforcing materials.

As an alternative to the use of a resin wetting basin 12 and holly board52 or roller 53 a, b arrangement, the filaments 1 could be pre-wetted byresin 14 by injecting the resin 14 adjacent the proximal ends 61 of thefilament channels 16 prior to contacting the fibers with the resin 22 inthe die 18 at the distal ends 62 of the channels 16. Alternatively, thefirst resin 14 could be applied via a spray-coating process.

The temperature of the first resin 14 in the basin 12 preferably will belower than the gelation temperature of the first resin in order toensure maximum wetting of the filaments by the resin. Thus, the resintemperature may be less than about 250-degrees Fahrenheit (F), morepreferably less than 150-degrees F, and most preferably less than about100F. In the case where the resin is a polymer melt, the temperatureshould be hot enough to melt the resin and maintain it at a viscositysufficiently low to enable wetting of the filaments, but cool enough tomaintain thermal stability of the polymer melt.

An alternative filament wetting system is described in U.S. Pat. No.6,955,735 to Walter W. Kusek, the entire disclosure of which isincorporated by reference herein.

Once the filaments 1 have been wetted with the first resin 14, they maypass into the crosshead die 18 for positioning, shaping and otherprocessing. Referring to FIG. 5A, the crosshead die 18 has a filamentinlet end 56, an intermediate extrusion inlet portion 58, and an outletend 30. The filament inlet end 56 may comprise a plurality of filamentchannels 16 configured to receive one or more of the filaments 1 orbundles of filaments and to guide them into desired positions within thecrosshead die 18. Thus, the filament channels 16 may act to place theindividual filaments 1, or bundles of filaments, in the positions theywill assume within the final thermoplastic profile 38. The filamentchannels 16 may each have a length L, and a first portion L1 of thelength L of each of the channels 16 may extend axially within thecrosshead die 18 so that the distal ends 62 of the channels 16 alignwith an inlet flow of the second resin 22. A second portion L2 of thelength L of each of the channels 16 may project axially outside of thedie 18 to allow for external cooling or other temperature control of thechannels, which will be explained in more detail later. As can be seenfrom FIG. 5A, the filament channels 16 may be of different lengths L andthey may extend different distances (L1) within the die 18.

Although it may be advantageous for the filament channels 16 to guidethe filaments 1 deep into the die 18, it is also important that thechannels 16 do not interfere with the intermixing of the filaments 1 andthe second resin 22. Thus, in one embodiment, the distal ends 62 of thefilament channels 16 may be spaced a distance D from the outlet end 30of the die 18. This distance D should be sufficient to ensure adequateinteraction between the second resin 22 and the pre-wetted filaments 1.As shown in FIG. 5A, the distance D may be a different value for each ofthe individual filament channels 16 (due to interaction with the curvedflow channel 70). Preferably distance D will be about 0.5 inches toabout 2-inches, more preferably about 1-inch to about 2-inches, and mostpreferably about 1.5-inches to about 2 inches. As will be appreciated,providing the appropriate distance D for each filament channel 16 isimportant to prevent a high pressure condition at the distal end 62 ofthe filament channels 16. Ideally, the difference between the forcegenerated by the forward motion of the pre-wetted filaments 1 throughthe die 18 and the force generated by the injection of the second resin22 should result in a backpressure of about zero at the distal ends 62of the filament channels 16, to prevent backflow of the second resin 22into the filament channels 16.

As shown in FIGS. 6A through 6K, the filament channels 16 may beprovided in any of a variety of orientations and arrangements to resultin a thermoplastic profile having a desired reinforcement scheme. Thus,square/rectangular (FIGS. 6A-D), cylindrical (FIGS. 6E-G), elliptical(FIG. 6H), triangular (FIG. 6I), and slotted (FIG. 6K), reinforcementconfigurations may be provided, depending upon the shape of the profile,and the type of reinforcement desired. The reinforcement can be appliedaround substantially the entire perimeter of the profile, or it may beapplied only to specific locations that are advantageous according to aparticular design. Examples of such placements in finished forms areshown in FIGS. 7A through 7F. A mandrel (not shown) may optionally beprovided within the overall die structure to enable processing of hollowor shaped parts of desired geometry.

With reference again to FIGS. 5A-C, the different stages of crossheaddie 18 will be described in greater detail with respect to the operationof the system. The die 18 of FIG. 5A has three individual “stages. Thefirst stage 64 may be a filament/resin feeding stage in which pre-wettedfilaments 1 are fed through the filament channels 16. The second stage66 may be a “transition stage” in which the filament (wetted with thefirst resin 14) contacts the second resin 22 at the output of the firstextruder 24. The third stage 68 may be a preforming/capping stage, inwhich the final profile preshape 28 is formed, the preshape being closeto the desired final shape, and the extruded capstock layer 36 isapplied. It is noted that this arrangement is slightly different fromthat illustrated in FIG. 1, in which the profile die 26 was shown aseparate die attached to the outlet 30 of the crosshead die 18. In thearrangement of FIG. 5A, however, the profile die 26 is provided as anintegral part of the crosshead die 18 (and thus the outlet 30 of thecrosshead die is shown as being downstream of the profile die 26).Either arrangement may be used as appropriate.

FIG. 5B shows the crosshead die 18 in which the third resin 34 isapplied to the profile preshape 28 at the profile die 26. FIG. 5C showsan alternative arrangement in which there is no inlet for theapplication of the third resin 34, and thus the profile preshape 28 isshaped within the profile die without a capping layer. Thus, thearrangement of FIG. 5C may be used to manufacture an uncapped profileproduct.

In order to obtain a highly efficient process, the temperature of thedie 18, and the materials contained therein, should be closelycontrolled to ensure that the transition from liquid resin to solidprofile is achieved at the desired place or region within the die, andthat the liquid resins (the first or second resins 14, 22) not gel (inthe case of the first resin 14) or solidify too early or too late. Itwill be appreciated that although these stages are described as beingdiscrete, they may rather comprise “zones” without discrete boundaries.

The second stage 66 of the die 18 may also have an internal channel 70configured to smoothly move the second resin 22 into intimate contactwith the filaments 1 and to move the combined resin/filament mixturesmoothly toward the die outlet 30, without generating unacceptable backflow of resin into the filament channels 16. The internal surfaces ofthe crosshead die 18 may further be designed to minimize or eliminateinternal static spots (also referred to as “dead spots”) within the diewhich may cause resin degradation, filament hang-up, or filamentbreakage.

As previously noted, when the pre-wetted filament 1 is fed into the die18 via the filament channels, each filament 1 (or filament bundle) maybe received within its own channel 16. Preferably, the filaments 1 willremain inside their respective channels for as long as possible prior tointerspersion of the filaments and the second resin. As previouslynoted, this may serve to accurately place the filaments at desiredlocations within the ultimate profile product. It also may serve toshield the individual filaments from the higher temperatures of thesecond stage 66 of the cross-head die 18 to ensure that the first resin14 does not begin to gel before it contacts the second resin 22. Thismay be important because if the first resin 14 solidifies too early inthe process, it can clog its associated filament channel 16.Additionally, early solidification can compromise the bond between thewetted filament 1 and the second resin 22, preventing intimate bondingbetween the first resin 14 and second resin 22 due to lack ofthermo-chemical reactivity, thereby resulting in a profile having lowermechanical strength characteristics.

Referring again to FIGS. 1 and 2, the second resin 22 may be introducedinto the crosshead die 18 at an extrusion inlet portion 56 of the die.The second resin 22 may be introduced into the die 18 at an input angleβ, which in FIG. 5A is about 90-degrees with respect to the flowdirection “A” of the filaments 1. More preferably, as shown in FIG. 1,the flow angle β may be less than 90-degrees so that the flow directionof the second resin has a flow component parallel to, and in the samedirection as, the movement direction “A” of the filaments 1. In onepreferred embodiment, the flow angle β is about 0-degrees to about60-degrees; in a more preferred embodiment, the flow angle β is about0-degrees to about 45-degrees; and even more preferably, the flow angleβ is about 0-degrees to about 40-degrees. Providing a non-perpendicularflow angle is advantageous because it minimizes or overcomesbackpressure in the filament channels 16 which may be caused by the highpressure flow of the second resin 22 into the die 18. As previouslynoted, such backpressure, if left unchecked, may lead to an undesirablebackflow of resin through the filament channels 16. Yet another benefitto such an angled introduction arrangement for the second resin 22 isthat it allows the associated first extruder 24 to be positioned closerto die 18, thus reducing the overall system floor-space.

Thus, orienting the flow of the second resin 22 so that a component ofits flow aligns with the flow direction “A” of the filaments 1 may serveto reduce the potential for the previously described backflow by addingthe forward momentum/movement of the second resin 22 through the die 18to the forward movement of the filament/first resin 1, 14. As noted, anoptimal balance may be obtained between the pressure at which the secondresin 22 is introduced into the die and the flow angle β at which thesecond resin 22 is introduced. This balance may be the point (or range)at which the force of forward movement of the second resin 22 exactlyovercomes the backpressure caused by the second extruder 35. At thisbalance point (or range), the resulting “pseudo-pressure” will approachzero. In one preferred embodiment, this resin input angle β may be about30-degrees to about 45-degrees.

As a further measure against backflow of resin into the filamentchannels 16, the clearance between the inner surface of the filamentchannels 16 and the associated filament 1 should be small. It will beappreciated that the ultimate clearance required to minimize oreliminate such backflow may be dependent upon the pressures inside thedie, as well as the viscosity and outer dimension of the filaments beingintroduced. Preferably, the clearance between the pre-wetted filaments 1and their respective filament channels 16 will be as small as possible,preferably approaching zero. In one embodiment, an additional quantityof resin 14 could be injected into the channels 16 with the filaments tominimize backpressure at the point where the filament meets the resin 22at the curved flow channel 70.

Further, the pressure at the distal ends 62 of the filament channels 16should be maintained as low as practical, preferably less than about 100pounds per square inch (psi), more preferably less than about 80 psi,and most preferably less than about 50 psi. These pressures may beroughly equivalent to the output pressure of the first extruder 24.

As previously noted, the die interior may have a curved flow channel 70which is configured to gently direct the flow of the secondthermoplastic resin 22 toward the die outlet 30. The degree and natureof the curvature of the flow channel 70 may selected based on theproperties of the resin (e.g., viscosity, molecular weight, molecularweight distribution). Exemplary shapes may be parabolic, logarithmic,etc. to provide smooth flow of the second resin 22 and result in evenwall thickness distribution for the profile preshape 28. As shown inFIG. 5A, the distal ends 62 of the filament channels 16 may each extenda different axial distance L1 within the crosshead die 18 so that thefilaments 1 are introduced at the edge of the curved flow channel 70.Thus, when the second resin 22 is introduced into the die 18, itsforward path may be urged gently forward by the contours of the flowchannel 70 to assume a flow direction parallel to that of the movementdirection A of the filaments 1 (FIG. 5A). The angled input orientationof the second resin 22, in combination with the curved flow channel 70,may also reduce the chance that static spots (dead spots) may forminside the die 18 which may cause resin degradation, or filament hang-upor breakage.

In order to obtain smooth operation of the system to obtain a desiredprofile shape having strong bonding between the individual resin andfilament components, close control should be maintained over thetemperatures of the first and second resins 14, 22 at the differentstages of the crosshead die 18. In the first stage 64, the temperatureof the filaments 1 (and importantly the first resin 14 which wets thefilaments 1) should be maintained below the gelation temperature of thefirst resin 14 to prevent or minimize the chance of clogging of thefilament channels 16. Preferably the temperature of the first stage 64will be less than about 250-degrees F, more preferably about 150-degreesF, and most preferably less than about 100-degrees F. It is noted thatthese temperatures are exemplary, and assume that the first resin 14comprises a vinyl plastisol resin. Where different resin compositionsare used for the first resin 14, appropriate temperatures should bemaintained in the first stage to maintain the first resin 14 in asubstantially liquid phase as it moves with the filaments through thefilament channels 16.

In the second stage 66, the pre-wetted filaments 1 are contacted by thesecond resin 22 and preferably the composite will begin to solidifyslightly due to the initiation of a thermo-chemical reaction (caused bythe second temperature) in the die between the first and second resins14, 22 (and within the resins themselves). Thus, the second stagerepresents the initial formation of what will become the ultimateprofile shape. The temperature of the second stage 66 should preferablybe higher than that of the first stage 64. In one embodiment, thetemperature of the second stage 66 should be about 300-degrees F toabout 450-degrees F, more preferably about 320-degrees F. to about400-degrees F, and most preferably about 350-degrees F to about380-degrees F.

As previously noted, it is important to ensure that the temperature ofthe first stage 64 is not so high that the first resin begins to gel tooearly (i.e. within the filament channels or adjacent their distal ends),which may cause the tubes to become clogged. Such clogging may cause theprocess run less efficiently, or to be stopped entirely. Also, it mayresult in inefficient or incomplete bonding between the first and secondresins, thus resulting in a profile having less than desired mechanicalstrength or other physical or aesthetic defect. Since the die 18 willtypically be made of metal (in some embodiments), a relatively high rateof conduction heat transfer may be expected from the higher temperaturesecond stage 66 to the lower temperature first stage 64. Although thetotal conduction may be relatively low when the system is initialized,heat transfer can be substantial once the system has been running for asignificant period of time. To minimize this heat transfer, a suitableinsulation layer may be provided between the first and second stages toprovide a thermal barrier. Examples of appropriate insulation materialsare polymer or polymer composites, ceramic materials, glass wool, andthe like.

In lieu of (or in addition to) providing an insulating layer between thefirst and second stages 64, 66, a cooling apparatus may be providedadjacent the first stage 64 to draw heat away from the filaments andfirst resin 14 to maintain the temperature sufficiently low to maintainthe resin 14 in a liquid state. Such cooling apparatus may comprise anair stream or air jet, a cooling jacket, an internal cooling channel,cooling fluid circulation channels, or the like. Use of an air streammay be particularly well suited for applications in which the proximalends 61 of the filament channels 16 extend out from the inlet end 56 ofthe die 18, since cool air may be blown across the proximal ends 61 ofthe channels 16 to cool the contained filaments/resin. In oneembodiment, the proximal ends 61 of the filament channels 16 may eachextend about 2-inches to about 3-inches out from the input end 56 of thedie 18 to allow cool air to be blown across the outer surface of thechannels. In the case where resin 14 is a molten thermoplastic resin, itmay be desirable to maintain the resin in a molten state as it entersthe filament channels 16. Further it may be desirable to contain amolten resin in an inert environment, such as contained within a closedprocess path, or under an inert gas atmosphere.

The third stage 68 of the die 18 may constitute a preforming/cappingstage, in which a final profile shape is “preformed” and where thecapstock extrusion is applied to further approach a final dimension. Assuch, the third stage 68 may comprise a profile die 26 (or feed block)in which the composite is formed into a shape close to the final profileshape, and the capstock extrusion is applied. Thus, a second extruder 35may be attached to the third stage 68 to co-extrude a third resin 34 onthe profile preshape 28. Unlike the second resin 22, the third resin 34is applied by an extruder or injector that can generate sufficientpressure to push the third resin 34 forward into the process path, andthus the concerns regarding backpressure within the die 18, etc. do notapply. As such, the second extruder 35 may be oriented to introduce thethird resin 34 into the profile die/feed block 26 at any desired angle.As noted previously regarding the first extruder 24, orienting thesecond extruder 35 at an acute angle with respect to the profiledie/feed block 26 may reduce the overall system footprint. As analternative to the co-extrusion process, the third resin 34 may also beapplied to the profile preshape 28 using an extrusion coating process.

It will be appreciated that known heating apparatus or apparatuses maybe used to input heat to the second and third stages 66, 68 of the die18 to within the desired temperature ranges.

The ultimate speed at which the profile 38 is drawn through the die 18may be adjustable, and may be based on chemical composition of the firstand second resins 14, 22, as well as size of the profile shape beingproduced. The inventors have achieved output rates of greater thannineteen (19) feet per minute using the disclosed system with vinylplastisol and thermoplastic materials and method for a profile having across-sectional area of about 0.42 square inches. It is expected thateven greater output rates may be achieved using the system, limitedprimarily by the curing time for the resins and the need to maintain thetemperature above the curing temperature of the resins long enough toform the profile preshape at the desired location within the die.

Although not shown, the die 18 may be provided in either a single ormultilayer arrangement. In one alternative embodiment in which amultilayer arrangement is used, the die may be configured so that thedifferent die layers can be rotated with respect to each other (eitherin opposite directions or the same direction at different speeds) togenerate angled filament reinforced profiles. As such, the resultingprofile may have a first layer of filaments oriented substantiallyparallel to the flow direction “A,” and a second layer of filamentsoriented non-parallel to the flow direction, “A.” Exemplary filamentorientations (i.e. around the circumference or perimeter of theprofile), could be angled with respect to the axis of the piece,circumferentially progressing along the length of the extrudate, orcould be or sine-shaped. Fibers could be wrapped in a crossing angularrelationship for progressive layers of the profile. Additionally, thenumber of filament strands provided in the non-parallel orientationcould be adjusted as desired. Preferably, the non-parallel direction canhave a directional component at least partially tangential to the flowdirection “A.”

It will also be appreciated that although the multi-stage crosshead die18 is illustrated as a single piece with multiple individual stages 64,66, 68, multiple individual dies may also be connected together toperform the same or similar functions of each of the described stages.

The disclosed system and method provide benefits of both extrusion andpultrusion processes, resulting in tight bonding between thereinforcements (filaments) and the substrate resin and thus providing athermoplastic profile having excellent mechanical strength anddurability. Thus, the resulting profile may have substantially improvedscrew and nail holding power, as well as superior resistance tocracking, splitting and filament separation, superior mechanicalstrength, in a lighter weight product having a lower filament loadingpercent. Good compatibility between the substrate resin (the secondresin) and the cap resin (the third resin) also may enhance the bondbetween the substrate resin and cap stock, resulting in a more durableand aesthetically pleasing product.

In other embodiments, shown in FIGS. 8A, 8B, the structural profile canbe produced using a pultrusion/molding process, such as apultrusion/injection molding process (FIG. 8A), or apultrusion/compression molding process (FIG. 8B), as describedseparately as following, and pultrusion/resin transfer molding.

FIG. 8A illustrates an injection molding arrangement for use with theinventive system. The system shown in FIG. 8A is substantially the sameas the system described in relation to FIG. 1, with all system elementsup to and including the second stage of the crosshead die 18 being thesame. The third stage of formation (that associated with the formationof the final profile shape), however, will occur within a mold 100.Thus, a transition zone 27 is provided between the die 18 and the mold100. The temperature in the transition zone 27 should be maintainedclose to the gel temperature of the first resin 14 and below thesolidification temperature of the second resin 22. Additionally, theresidence time of the composite material within the transition zone 27should be as short as possible to ensure that solidification does notoccur prior to injection of the material into the mold 100. Thus, theentire melt (including filaments, and first and second resins 14, 22)will be injected into the mold 100 under the pressure provided by theextruder 24. The shape of the mold 100 may be selected, as desired, toproduce products for specific applications, such as siding panels, fencepicket parts, end caps, joints, hinges, trim boards for interior andexterior decoration, synthetic roofing shingles, slates, shakes orpanels, etc.

After the material is molded in the mold 100, the temperature of themold 100 may be maintained at or above the solidification temperature ofthe second resin 22 for a desired time period to allow for sufficientcuring or solidification of the first plastisol resin, or to allowsufficient time for bonding between the filament 1 and the first resin14, and between the first resin 14 and second resin 22. The temperaturemay then be decreased to the solidification temperature of the secondresin 22 using a cooling system (not shown). The molded product will besolidified by bringing it to a temperature below that of the meltingtemperature of the second resin 22. The product will then be de-molded,the mold 100 will be closed, and a new molding cycle will occur. Thecycle time for each molding process may be adjusted to suit the resinsused, to achieve sufficient bonding, and to enhance overall processproductivity.

The mold 100 may be a single cavity or multi-cavity mold. The number ofthe cavities may be determined by the resin used, the cycle time, andthe output rate desired. The transition zone 27 of the die may be aninjector where the first resin wetted filament and the second resin arecontinuously injected and accumulated in the barrel of the injector.When the cycle time is reached and the barrel is full for discharge, apiston may be used to inject the material to the mold cavity. The timeinside the injector may be controlled and optimized so that the firstresin 14 is not pre-solidified. As previously noted, the forwardmovement of the material is not generated by the combination ofextrusion and pulling, as would be the case with a pultrusion apparatus,but is generated solely by the extrusion of the second resin 22 into thetransition zone 27.

FIG. 8B illustrates a compression molding arrangement for use with theinventive system. The system shown in FIG. 8B is substantially the sameas the system described in relation to FIG. 1, with all system elementsup to and including the second stage of the crosshead die 18 being thesame. As with the injection molding arrangement (FIG. 8A), the thirdstage of formation (that associated with the formation of the finalprofile shape) will occur within a mold 200. Thus, the temperature inthe transition zone 27 should be lower than the gel temperature (orbelow the solidification temperature) of the first resin 14 (in the caseof a plastisol resin system). Additionally, the residence time of thematerial within the transition zone 27 should be as short as possible toensure that solidification does not occur prior to introduction of thematerial into the mold 200. The melt will be extruded out of the sheetdie 29 and will be then cut using a cutting blade 31 to a desired size.The resulting cut pieces 33 may then be transferred away from the die 29by a belt 35 and transported to a mold, for example, by being picked upby an automated robot arm 37, and placed into a compression mold 200.The shape of the compression mold may be selected, as desired, toproduce products for specific applications. Such applications mayinclude, siding panels, fence picket parts, end caps, joints, hinges,trim board for interior and exterior decoration, synthetic roofingshingles, slates, shakes or panels, etc.

After the material is molded in the mold 200, the temperature of themold 200 may be maintained at or above the solidification temperature ofthe second resin 22 for a desired time period to allow for sufficientcuring or solidification of the first plastisol resin, or to allowsufficient time for bonding between the filament 1 and the first resin14, and between the first resin 14 and second resin 22. The temperaturemay then be decreased to the solidification temperature of the secondresin 22 using a cooling system (not shown). The molded product will besolidified by bringing it to a temperature below that of the meltingtemperature of the second resin 22. The product will then be de-molded,the mold 200 will be closed, and a new molding cycle will occur. Thecycle time for each molding process may be adjusted to suit the resinsused, to achieve sufficient bonding, and to enhance overall processproductivity. The mold 200 may be a single cavity or multi-cavity mold.The number of the cavities may be determined by the resin used, thecycle time, and the output rate desired.

A specific compression molding arrangement is disclosed in copendingU.S. patent Ser. No. 11/227,009 to MacKinnon et al., Titled “Process ofand Apparatus for Making a Shingle, and Shingle Made Thereby”, theentire contents of which application is incorporated by referenceherein.

As with the injection molding arrangement, forward movement of thecomposite is not generated by the combination of extrusion and pulling(as it is in the previously-described pultrusion/co-extrusionembodiments, but instead purely generated by the extrusion of the secondresin 22 into the sheet die 29.

Structural profiles produced using the disclosed method and apparatusmay have any of a variety of cross-sectional shapes, such as round,square, rectangular, with reinforced beam, etc. These profiles may beuseful for building and construction applications, including siding,roofing, fence, decking, window profiles, pipe, post, and for structuralapplications, including railing on bridges, light posts, highwaysignage, roadside marker posts, etc. Further, the profiles producedusing the described process may have substantially higher strength ascompared to current filament reinforced pultrusion and extrusionprocesses, so that the thicknesses of the profiles may be minimized, andthe need for additional reinforcement (e.g. ribs, reinforcing rods,etc.) may be minimized or eliminated. For example, the modulus ofelasticity of the profile products produced using the disclosed systemand method may be at least 2,000 kpsi, preferably 2,500 kpsi, and mostpreferably 3,000 kpsi.

The disclosed system provides substantial benefit over conventionalsystems and methods for thermoplastics pultrusion because it providesfor fast wet-out of filaments (using the filament pre-wettingarrangement described in relation to FIGS. 3A-3E). This is an advantageover conventional thermoplastics pultrusion techniques in whichfilaments are wetted with molten thermoplastic materials, which may beof high viscosity and thus may not allow wetting at the higher ratesprovided by the disclosed system. Additionally, the disclosed system andmethod provide for final shaping and sizing to occur outside thecrosshead die 18, which minimizes the chance for damage to the dieand/or extrudate.

Materials suitable for use as the first resin 14 include PVC plastisol,polyester plastisol, styrenic plastisol, high melt flow indexpolyolefins, etc. Examples of suitable high melt flow index polymersinclude polyolefins and acid containing olefin copolymers having a highmelt flow index, polyurethanes, and acrylic acid copolymers. Materialssuitable for use as the second and third resins 22, 34 includepolyolefins such as HDPE, LDPE, LLDPE, UMWHDPE, polypropylenehomopolymers and copolymers, impact modified polystyrene, AcrylonitrileButadiene Styrene (ABS), polyamine, polyesters, polycarbonate, PVC(polyvinyl chloride), acrylic-styrene-acrylonitrile (ASA), PMA, PMMA,PEA, PEMA, PBA, PBMA, EVA, PVA, EVOH, maleic anhydride modifiedpolyethylenes), maleic anhydride) modified polypropylenes, ionomerizedacid containing polymers, and combinations or mixtures thereof.

The first and second extruders 24, 35, used for extruding the second andthird resins 22, 34 respectively, can be single screw extruders,co-rotating twin screw extruders, or counter rotating twin screwextruders. The screws for the twin screw extruders can be designed to beintermeshing, non-intermeshing, according to the resin used.Additionally, the first extruder may deliver to the die 18 a combinationof the first resin 22 and a suitable filament-reinforcing material,which may provide additional strength to the produced profile. Thefilaments added to the second resin 22 within the first extruder 24 maycomprise continuous filaments, long filaments, or chopped filaments, asdesired. Additionally, fillers may be used, such as CaCO₃, talc,wollastanite, mica, clay, fly ash, volcanic ash, slate dust, woodflours, flax, rice hulls, cork, kenaf, or combinations and mixturesthereof. The extruders 24, 35 may have heating or cooling elements toensure that the extruded resin flows smoothly through the extruder andthrough the die 18.

Suitable materials for filaments 1 include A-glass, B-glass, C-glass.D-glass, E-glass filament, S-glass filament, carbon filament, steelfilament, polyolefin filaments including HDPE, LDPE, UMWHDPE, LLDPEfilament, polypropylene (PP) filaments, Aramid filaments, polyesterfilaments, and combinations thereof. Furthermore, invention is notlimited to the use of filaments or bundles, and thus flat forms ofreinforcement such as scrim, mats, felt, etc., are also contemplated foruse. Where flat forms are used, the filament channels 16 may be sized asappropriate to accommodate such shapes.

Appropriate additives for the first, second and third resins 14, 22, 34include thermal stabilizers, UV absorbers, UV stabilizers, hinderedamine light stabilizers (HALS), antioxidants, pigments, colorants, dyes,color concentrates, processing aids, plasticizers, anti-statics,nucleating agents, anti-blocking agents, and mixtures or combinationsthereof.

Example

A PVC-Glass fiber/PVC Plastisol-Acrylic cap stock profile extrusion wascarried out using a 3.5″ Davis Standard single screw extruder as a mainextruder for PVC substrate extrusion, a three stage 0.705″×0.705″crosshead die, with a square hole in the center, a 1.5″ Polytrudersingle screw extruder, a vacuum calibration system, a fiber creel, and aplastisol resin bath. The substrate resin (second resin 22) was a rigidPVC material having a composition as shown in the table below.

Parts by Material weight Source of material OxyVinyls 216 Polyvinyl100.00 OxyVinyls, Dallas, TX chloride Mark 1900 Stabilizer 1.50 ChemturaCorporation, Middlebury, CT Kronos 2073 Titanium dioxide 1.00 Kronos,Inc., Cranbury, NJ Rheolub 250 Lubricant 0.90 Honeywell, Morristown, NJAC 629 A Lubricant 0.15 Honeywell, Morristown, NJ Loxiol G60 Lubricant0.50 Cognis, Ambler, PA Ca St Calcium stearate 0.50 Paraloid K 400 Flowaid 6.50 Rohm and Haas, Spring House, PA Omyacarb UFT Calcium 3.00 OmyaInc., Alpharetta, carbonate Georgia TOTAL phr 114.05The glass fiber was grade 673 from Vetrotex; the cap stock (third resin34) was Solarkote from Arkema, Inc.; the plastisol resin (the firstresin 14) was Structural Engineered Plastisol (SEP) resin product numberZ0423B03 RDP-00016 available from Rutland Plastic Technologies, 10021Rodney Street, Pineville, N.C. 28134. Eight strands of glass fiber werefirst fed into eight separate channels of the die without contacting theplastisol resin, and pulled through the crosshead die and calibratorusing a puller. The PVC substrate was then extruded through thecrosshead die, and when the resin extruded out of the die andcalibrator, the profile along with the glass fiber was pulled throughthe cooling tank and puller, and cutting saw. When the process wasstable, the middle holly board was slid into the bath where the SEPresin submerged the glass fiber. The profile then was extruded withglass fiber and SEP resin and the PVC matrix substrate. The profile wascalibrated, cooled and cut to length for sample collection and testing.The samples were collected at different speeds, with and without SPEresin, and with and without cap stock. The samples were then tested forthe stiffness, strength, elongation, screw holding power, andcoefficient of linear thermal expansion (CLTE).

Table 1 lists maximum strength and displacement at yield for the wholepart (profile) tested using a three point bending test. The three pointbending tests were conducted using an Instron machine model 4400R,following ASTM D790. Tests were conducted at room temperature and 50%relative humidity. The span for the fixture was set at 6 inches, andcross-head speed was fixed at 0.085 in/minute.

Max Load Displ at Yield Samples [lbf] [in] 5.86% glass fiber (GF), 6.8feet per 484 0.4889 minute (fpm), no cap 5.59% GF, 5.1 fpm, no cap 5670.4054 5.99% GF, 3.4 fpm, no cap 626 0.448 5.62% GF, 13.6 fpm, no cap474 0.4372 5.44% GF, 13.6 fpm, Tdie = 370° F., no cap 443 0.4507 4.39%GF, 6.8 fpm, with cap 605 0.3544 0% GF, 6.8 fpm, with cap 284 0.4515Conventional Profile, 55% GF 326 0.1073

Table 2 lists modulus of elasticity, displacement at yield, and strengthat yield for the milled test bars using a three point bending test. Thethree point bending tests were conducted at the same conditions asdescribed above in regards to Table 1, following ASTM D790. The sampleswere cut from produced picket samples into rectangular bars havingdimensions of approximately 0.7×0.125×6 inches. The span for the testfixture was calculated at sixteen times the depth of the sample,resulting in approximately 2 inches.

MOE Stress at Yield Displ at Yield Samples [kpsi] [kpsi] [in] 5.86%glass fiber (GF), 6.8 feet 402 9.5 0.438 per minute (fpm), no cap 5.59%GF, 5.1 fpm, no cap 453 11.1 0.474 4.39% GF, 6.8 fpm, with cap 325 10.10.523 0% GF, 6.8 fpm, with cap 280 7.3 0.469 Conventional Profile, 55%GF 1555 36.9 0.219

Table 3 lists the screw holding power. Screw holding power was tested onwhole profile samples, approximately 6-inches in length, using anInstron machine model 4400R at room temperature. For each sample, a ⅛″diameter, 1-¾″ long sheet metal screw was installed in a hole predrilledin the center (lengthwise) of the sample. The sample was then grippedwith a metal piece and the screw was pulled by the upper gripper of theInstron machine, until the screw was completely pulled out. The maximumload was then recorded.

Screw Holding Power Samples [lbf/in] 5.86% glass fiber (GF), 6.8 feetper 2465 minute (fpm), no cap 5.59% GF, 5.1 fpm, no cap 2167 5.99% GF,3.4 fpm, no cap 2104 5.62% GF, 13.6 fpm, no cap 2161 5.44% GF, 13.6 fmp,Tdie = 370° F., no cap 3167 4.39% GF, 6.8 fpm, with cap 2621 0% GF, 6.8fpm, with cap 2833 Conventional Profile, 55% GF 675

Table 4 lists Coefficient of Linear Thermal Expansion (CLTE). CLTE testswere conducted using an Electronic Ball Deformeter manufactured by CEBTPcompany of France, to measure the thermal dilatation on a profile(length of about 8-inches) between two temperatures, 60° F. and 150° F.The average of the two CLTE values was then taken as the CLTE at anaverage temperature of 105° F.

Samples CLTE, ×10⁻⁶ (degree F.)⁻¹ E-glass, at 68° F. 3 Polypropylene, at68° F. 56 PVC, at 68° F. 47 4.39% glass fiber (GF), 6.8 feet per 15.9minute (fpm), with cap, at 105° F. 0% GF, 6.8 fpm, with cap, at 105° F.24.6 Conventional Profile, 55% GF, at 105° F. 3

Although the invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly to include other variants and embodiments ofthe invention that may be made by those skilled in the art withoutdeparting from the scope and range of equivalents of the invention.

1. A method for manufacturing a reinforced thermoplastic structure,comprising: providing a plurality of reinforcing filaments; wetting thereinforcing filaments with a first thermoplastic resin; introducing thereinforcing filaments with the first thermoplastic resin into a firstportion of a die and maintaining said thermoplastic resin at a firsttemperature; introducing a second thermoplastic resin into a secondportion of the die; contacting the second thermoplastic resin with thereinforcing filaments and the first thermoplastic resin within thesecond portion of said die; and heating the first and secondthermoplastic polymer resins to a second temperature to form a partiallysolidified reinforced thermoplastic structure having a predeterminedouter shape; and wherein the first temperature is a value below thesolidification temperature of the first thermoplastic resin and thesecond temperature is a value above the solidification temperature of atleast the first thermoplastic resin.
 2. The method of claim 1, furthercomprising contacting the partially solidified reinforced thermoplasticstructure with a third thermoplastic resin to form a capping layer on anexterior surface of the reinforced thermoplastic structure.
 3. Themethod of claim 1, wherein the predetermined outer shape comprises apreshape form, the method further comprising directing the partiallysolidified reinforced thermoplastic structure through a sizing die orcalibrator to impart a final form to the structure.
 4. The method ofclaim 1, wherein the step of introducing said reinforcing filaments withthe first thermoplastic resin into the first portion of a die furthercomprises providing the die with a filament channel sized and configuredto receive the reinforcing filaments with the first thermoplastic resin,the filament channel further configured to direct the filaments to anintroduction location of the second thermoplastic polymer within thedie.
 5. The method of claim 4, further comprising the step ofmaintaining a temperature of an interior surface of the filament channelbelow the solidification temperature of the first polymer while thefirst polymer is located within the filament channel.
 6. The method ofclaim 5, wherein the filament channel has a proximal input end and adistal output end, and the distal output end is located adjacent to, orwithin, the second portion of the die, the distal output end beingpositioned to place the associated filaments at a predeterminedcross-sectional location within the reinforced thermoplastic structure.7. The method of claim 4, further comprising providing a plurality offilament channels, the plurality of filament channels being positionedwithin the die to place the reinforcing filaments at predeterminedlocations adjacent the second portion of the die to produce a reinforcedthermoplastic structure having a predetermined reinforcement scheme. 8.The method of claim 1, wherein the second thermoplastic resin isintroduced into the second portion of the die in a first flow direction,the first flow direction forming a first angle with respect to amovement direction of the reinforcing filament and the firstthermoplastic resin through the die, and wherein the first angle is lessthan 90 degrees so that a component of the first flow direction isparallel to the movement direction.
 9. The method of claim 2, whereinthe first thermoplastic resin comprises plastisol, and the secondthermoplastic resin comprises polyvinylchloride which is introduced intothe second portion of the die at melt state.
 10. The method of claim 2,wherein the third thermoplastic resin comprises an acrylic materialwhich is introduced into the third portion of the die at melt state. 11.The method of claim 1, further comprising using a first extruder to meltthe second thermoplastic resin, and providing a quantity of reinforcingmaterial into the first extruder with the second thermoplastic resin.12. The method of claim 1, wherein the first temperature is in the rangeof about 70° F. to about 250° F. and the second temperature is in therange of 300° F. to about 380° F.
 13. The method of claim 1, wherein thereinforcing filaments comprise a filament bundle.
 14. The method ofclaim 1, further comprising introducing the partially solidifiedreinforced thermoplastic structure into a mold cavity and forming afinal form to the structure within the mold.
 15. A method formanufacturing a reinforced thermoplastic structure, comprising:providing a reinforcing filament; wetting the reinforcing filament witha first thermoplastic resin; introducing the reinforcing filament withthe first thermoplastic resin into a first portion of a die andmaintaining said thermoplastic resin at a first temperature; introducinga second thermoplastic resin into a second portion of the die;contacting the second thermoplastic resin with the reinforcing filamentwetted by the first thermoplastic resin within the second portion ofsaid die; transporting the first and second thermoplastic polymer resinsthrough the second portion of said die while forming the first andsecond thermoplastic polymer resins into a reinforced thermoplasticstructure having a predetermined outer shape; and exposing thereinforced thermoplastic structure to a zone having a secondtemperature; wherein the first temperature is a temperature at which thefirst thermoplastic resin is in a stable liquid state and the secondtemperature is a value at which the first thermoplastic resin can atleast partially solidify.
 16. The method of claim 15, further comprisingcontacting the at least partially solidified reinforced thermoplasticstructure with a third thermoplastic resin to form a capping layer on anexterior surface of the reinforced thermoplastic structure.
 17. Themethod of claim 15, wherein the predetermined outer shape comprises apreshape form, the method further comprising directing the partiallysolidified reinforced thermoplastic structure through a sizing die orcalibrator to impart a final form to the structure.
 18. The method ofclaim 15, wherein the step of introducing said reinforcing filament withthe first thermoplastic resin into a first portion of a die furthercomprises providing the die with a filament channel sized and configuredto receive the reinforcing filament with the first thermoplastic resin,the filament channel further configured to direct the filament to anintroduction location of the second thermoplastic polymer within thedie.
 19. The method of claim 18, further comprising the step ofmaintaining a temperature of an interior surface of the filament channelbelow an upper solidification temperature of the first polymer while thefirst polymer is located within the filament channel.
 20. A method formanufacturing a reinforced thermoplastic structure, comprising:providing a plurality of reinforcing filaments; wetting the reinforcingfilaments with a first thermoplastic resin; introducing the reinforcingfilaments with the first thermoplastic resin into a first portion of adie and maintaining said thermoplastic resin at a first temperature;introducing a second thermoplastic resin into a second portion of thedie; contacting the second thermoplastic resin with the reinforcingfilaments and the first thermoplastic resin within the second portion ofsaid die; heating the first and second thermoplastic polymer resins to asecond temperature to form an at least partially solidified reinforcedthermoplastic structure having a predetermined outer shape; andcontacting the reinforced thermoplastic structure with a thirdthermoplastic resin to form a capping layer on an exterior surface ofthe reinforced thermoplastic structure; wherein the first temperature isa value below the solidification temperature of the first thermoplasticresin and the second temperature is a value above the solidificationtemperature of the first thermoplastic resin.